Hollowing out a planet

[Lvl 2 Expert]

Yeah, but it's supposed to be a tragedy because they're also living on the planet and therefore they destroyed their home. They'd have killed themselves from this residual heat in the atmosphere long before they got close to mining out enough for the planet to collapse in your scenario.

Well, tragedy is a value judgement. You probably wouldn't mind having to demolish your house (your literal brick and mortar house) because you've found a rich deposit of [insert your favorite expensive resource here] underneath it and can now afford a palace from the advances companies are throwing at you alone.

People from two centuries later may not like the empty hole quite as much, but maybe you invested your earnings really wisely in a fund that turned the mine into a themepark nature reserve orphanage combination and everyone lives happily ever after?


Okay, back in character, I look around, do I see any roughly planet sized themepark nature reserve orphanage habitats in this system?

[Bohandas]

on human timescales (seconds to minutes to hundreds of years) it will act like solid rock does (as in: highly elastic). If you hit it with a hammer, it will fracture, and seismic waves propagate through the mantle in the exact same manner they do on the crust.

However, on geologic timescales (Hundreds of millions to billions of years), the mantle acts as a viscous fluid. It will flow very slowly (through molecular-level processes called creep) in both newtonian and non-newtonian manners.

So it's like asphalt, but moreso?

[factotum]

Why not build towering insulated tubes for the material to pass through on its way skyward? They're bound to be removing a great deal of unwanted rock and other matter - let them build their own volcanoes that pierce the upper atmosphere and have the collecting and processing equipment located at the peaks.

Building a tower that reaches right to the edge of the atmosphere is a non-trivial problem, especially when you need it to be airtight and also survive stuff being fired through the middle at orbital velocities.

[Yoshi-TRM]

So it's like asphalt, but moreso?

Yes; pretty much all solid rock is like asphalt, only moreso.

[Rogar Demonblud]

Some of the objections raised can be solved fairly trivially. People don't mine the asteroids because there aren't any. In fact, their may not be any other planets at all (thereby evading the question of why not mine them out and leave your living space alone). And if you have this much material available to you that the planet is in danger of collapsing in on itself, you probably have an orbital ring with multiple elevators to it. Note back, you probably don't have a significant moon either for the same reason as the planets, which would ease the gravitic stresses on the ring. And if you have a ring and maybe O'Neill cylinders as well (might as well go whole hog), well, who lives on them? The 1%ers? The top 5%? Is it just the people who don't care so much about what the surface of the planet is like, because they got theirs?

Really, there are a lot of details and worldbuilding to be found in these and other questions.